Dual-process theories argue that cognitive processes, and executive functions in particular, underpin controlled, goal-directed, decisions about food intake and choice. A considerable amount of research has been devoted to understanding the role of one executive function, inhibitory control, in appetite control. In addition, there has been interest in whether inhibitory control can be trained to improve dietary decisions. A systematic review and meta-analysis, however, casts doubt over the efficacy of training inhibitory control to change eating behaviour (Chapter 2). The importance of another executive function to eating behaviour, working memory, has been less well-studied. The aim of this thesis was to assess the role of working memory in food-related decision making in healthy volunteers and patients with type 2 diabetes. The results of Study 1 (Chapter 3) suggest that visuospatial working memory is important for decisions about the consumption of low energy dense foods and dieting success. The findings from Study 1 also provide support for the suggestion that dietary restraint has detrimental effects on central executive functioning. Study 2 (Chapters 4 and 5) found that working memory training can improve working memory and non-trained aspects of working memory in adults with type 2 diabetes. Transfer effects to eating behaviour were limited to those high in restraint (the higher the restraint the greater the reduction in saturated fat intake from pre-training to post-training). The results from Study 3 (Chapter 6) suggest that cognition (including one component of working memory) may be less important to food intake decisions in the context of other demographic, physical and psychological health factors. The importance of working memory to food intake decisions can be observed in controlled laboratory experiments. However, further research is needed to establish whether training working memory is a useful strategy to help bring about behaviour change to improve dietary choices.